RG 307 Revised January 2013

ClematisClematis are often referred to as the queen of the flowering vines. Plants in this versatile genus produce single or double flowers from May to October in a variety of colors. Sepals—not petals —make up the colorful portion of the flower. The petal-like sepals may be thin, wide, pointed, rounded, crinkled, twisted, or even crimped. They may be marked with center bars, stripes, or vivid shadings. Flower form varies from nodding, pitcher-shaped, bell-shaped, or star-shaped, to the familiar large, flat, erectly held blossoms. Flowers may have contrasting colored stamens or no stamens at all. Small flowered varieties (cultivars) offer a range of fragrances lacking in the large flowered varieties.

Some clematis can grow 8 to 12 feet in a single season, others reach a height of only 2 to 4 feet. There are more than 250 species of clematis and several hundred cultivars. Not all clematis are hardy in Iowa, but numerous species and cultivars can be successfully grown in the state.

Types of ClematisVining clematis can be divided into three groups.

Group 1: Blooms on the previous season’s growth (old wood)Examples: Clematis alpina and Clematis macropetala

The earliest clematis bloom in May. Flowers develop from buds located on the previous season’s growth.

This group is the most difficult to succesfully grow in Iowa because the vines may suffer extensive dieback over winter and produce few, if any, flowers. To encourage bloom, remove the vines from their support, lay them on the ground, and cover with several inches of mulch. Wait until bud break before pruning, then prune back to live wood.

Group 2: Flowers on both old and new growth Examples: ‘The President’, ‘Henryi’, and ‘Ramona’

The second group of clematis blooms twice. Large flowers are produced from May to July on the previous season’s growth. In late summer, plants bloom on the current year’s growth.

In early spring, prune out the dead wood. Spring blooms will be sparse if plants suffer extensive winter dieback. Plants will bloom more heavily in late summer.

Group 3: Flowers on new growthExamples: Clematis viticella, Clematis terniflora, and large flowered hybrids such as Clematis × jackmanii, ‘Ernest Markham’, and ‘Hagley Hybrid’

The third group of clematis flowers on the current year’s growth (new wood). Vines produce one main flush of bloom (sometime from late May to September). Because they bloom on current year’s growth, these are the most reliable performers in Iowa.

Pruning is relatively easy. Vines can be cut back to within 6 to 12 inches of the ground in late winter/early spring. An alternative method is to wait until bud break in spring and prune back to the uppermost new growth.

Growing tipsClematis thrive in rich, well drained soils with at least 6 hours of sunlight each day and 1 inch of water per week.

When planting, dig a generous-sized hole and fill with a mixture of soil and compost or moistened peat. Do not add lime unless your soil is highly acidic. Clematis prefer soils with slightly acidic to neutral pH levels. Plant the crown 1 to 2 inches below the soil surface. Water well and mulch with 2 to 3 inches of organic material such as wood chips or shredded bark.

A mulch provides winter protection for the crown and keeps the root system cool during summer heat.

After planting, trim to 12 inches or to a pair of low buds to encourage multiple branching and additional shoots. Fertilize established plants with a balanced all-purpose garden fertilizer (such as 10-10-10) in spring.

SupportClematis climb by twisting their petioles or leaf stalks around a support. They can be grown on trellises, fences, lampposts, deck rails, and other structures. Clematis also can be allowed to climb over shrubs, small trees, tree stumps, and rock piles. When planting near a non-living support, allow at least a foot between the support and the plant. Near shrubs, trees, and other living supports, locate plants at least 2 feet away from the support. New growth will wind through the support towards the light. Clematis do not possess tendrils or aerial rootlets; you may need to help young plants start to vine where you want them.

PestsClematis don’t have serious insect pests. However, clematis wilt is an occasional problem. Affected vines wilt suddenly and then die. Dead vines should be cut at ground level, removed, and destroyed. Clematis wilt rarely kills the entire plant. Affected plants usually send up new shoots.

Clematis in vasesClematis are excellent fresh cut flowers and can last four days or longer. Look for flowers that have just opened or are only three-fourths open on thick, strong stems. Three choices include ‘Beauty of Worcester’, ‘The President’, and ‘Nelly Moser’. Many clematis also form attractive seed heads.

Best for Iowa Suggested clematis species for Iowa include (flowering occurs on the wood type as indicated):

• Clematis alpina–blue flowers (old) • Clematis integrifolia–indigo blue flowers (new) • Clematis macropetala–lavender blue flowers (old)• Clematis orientalis–yellow flowers (new) • Clematis recta–white flowers (new) • Clematis terniflora–white flowers (new) • Clematis texensis–scarlet flowers (new) • Clematis viticella–purple flowers (new)

Suggested cultivars according to color include (flowering occurs on the wood type as indicated):

Purple—‘Gipsy Queen’ (new), jackmanii ‘Superba’ (new), ‘The President’ (old, new)

Blue—‘Mrs. Cholmondeley’ (old, new), ‘Ramona’ (old, new), ‘Lord Nevill’ (old, new), ‘Ascotiensis’ (new), ‘Betty Corning’ (new)

Red—‘Madame Edouard Andre’ (new) ‘Lincoln Star’ (old, new), ‘Ernest Markham’ (new), ‘Niobe’ (new), ‘Ville de Lyon’ (new), ‘Rouge Cardinal’ (old, new)

White—jackmanii ‘Alba’ (new), ‘Henryi’ (old, new), ‘Marie Boisselot’ (old, new)

Pink—‘Comtesse de Bouchaud’ (new), ‘Hagley Hybrid’ (new), ‘Bees Jubilee’ (old, new), ‘Duchess of Albany’ (new)

Bicolor—‘King Edward VII’, (old, new) ‘Nelly Moser’ (old), ‘Star of India’ (new)

Sources Busse Gardens 17160 - 245th Ave. Big Lake, MN 55309 www.bussegardens.com

Greer Gardens 1280 Goodpasture Island Road Eugene, OR 97401 www.greergardens.com

Bluestone Perennials 7211 Middle Ridge Road Madison, Ohio 44057 www.bluestoneperennials.com

Song Sparrow Perennial Farm 13101 East Rye Road Avalon, Wisconsin 53505 www.songsparrow.com

Wayside Gardens 1 Garden Lane, Hodges, SC 29695-0001 www.waysidegardens.com

For more information For more information on selection, planting, cultural practices, and environmental quality, contact your Iowa State University Extension county office, or visit one of these ISU websites:

https://store.extension.iastate.edu/ http://www.yardandgarden.extension.iastate.edu http://www.reimangardens.iastate.edu

Revised by Richard Jauron, extension horticulturist. Originally written by Sherry Rindels, former extension horticulturist.

…and justice for allThe U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic infor-mation, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at 202-720-2600 (voice and TDD). To file a complaint of discrimination, write to USDA, Director, Office of Civil Rights, 1400 Independence Avenue SW, Washington, DC 20250-9410, or call 800-795-3272 (voice) or 202-720-6382 (TDD). USDA is an equal opportunity provider and employer.

Issued in furtherance of Cooperative Extension work, Acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture. Cathann A. Kress, director, Cooperative Extension Service, Iowa State University of Science and Technology, Ames, Iowa.